Fabric mesh reinforced thermoplastic membranes have been available for some time for a number of uses, including, for example, for use as a roofing membrane, and pond, reservoir, pit and canal liners. These membranes typically have a fabric reinforcing mesh sheet encapsulated therein so that it is not visible in the final product. There are various conventional methods for making these mesh-reinforced membranes. One conventional method involves extruding molten thermoplastics onto one side of a fabric mesh sheet to secure the fabric mesh to one half of the thermoplastic membrane. The resulting composite is then heated and a second layer of molten thermoplastic is extruded onto the opposite side of the fabric mesh sheet, resulting in a thermoplastic membrane with an integrated fabric mesh reinforcing sheet.
Another conventional method of making fabric mesh reinforced thermoplastic membranes involves drawing a fabric mesh sheet through an extrusion device where molten thermoplastic is extruded onto both sides of the sheet simultaneously, and the molten membrane is then drawn through a series of calendar rolls to help form the membrane. The membrane may then be drawn over a cooling bed and exposed to ambient air to return the thermoplastic to an ambient temperature.
In some cases, when relatively narrow reinforced thermoplastic membranes are required, a single reinforced membrane will be created and then cut in half to produce two reinforced membranes of the desired width. By cutting a wider reinforced membrane in half to make two narrower membranes, the output of the manufacturing process is doubled relative to a production method where a single narrow reinforced membrane is produced. However, this method results in a rough edge where the reinforced membrane is cut to create two narrow membranes. Thus, unlike the uncut reinforced membranes, the narrow reinforced membranes formed from cutting a single membrane do not have fully encapsulated edges, also known as gum edges.
There is therefore a need for a method of manufacturing narrow mesh-reinforced thermoplastic membranes that have fully encapsulated edges extending longitudinally along both sides of the membrane, without sacrificing the efficiency available from existing methods of manufacture.